A new year (and a new budget) may inspire some marketers to consider switching email service providers. While price is always an issue, there are other variables that matter more, said Polina Polishchuk, technology editor at NextAdvisor.com, an independent research site. "A more expensive service doesn't necessarily mean a better service," she said. Polishchuk suggested asking potential ESPs how they stack up on the following:

Contacts allowance: If you have a large subscriber list, you'll need a company that caters to it; however, even smaller companies that anticipate big subscriber growth should ask about contact limits as well as any costs associated with exceeding those limits, Polishchuk said. In addition, ESPs should be able to give you details about their email volume and how they will "warm up" your server. Any company that's simply going to batch and blast your entire subscriber list isn't thinking enough about reputation.

Deliverability rate: This is one of the most important things companies should consider when choosing an ESP: Customers can't respond to undelivered offers and emails, she said. Ask about deliverability rates within your vertical and compare that rate to the industry average.

List growth features: Does the ESP have sign-up-form creation? Does it offer "forward to a friend" or social options? These methods of list growth should be built in to help you keep your list growing and evolving, Polishchuk said.

Customer service: Even the most experienced marketers need lots of help when migrating an email program from one ESP to another, she said. Find out about customer service options at the ESP being considered, and ask to see customer referrals and feedback. Another topic under the customer service heading: What kinds of templates and tools are available? While this might not be important if you have an in-house designer, most companies can benefit from automated design features that make your messages more appealing.

Analytics: Every marketer knows how important analytics are to the health and success of a new email marketing program. Analytics should be available, but they should also be easy to read and download so you can integrate metrics into your existing marketing analytics program, she said. "Integration with Google Analytics will also be important to many people," Polishchuk said.